INTRODUCTION:

Wound infection has always been a major complication of surgery and trauma. Despite current pre-operative preparation, operative technique, and antibiotic prophylaxis, post-operative wound infections remain a serious problem¹.Surgical infections are the third most commonly reported nosocomial infections and they represent around 25% of all nosocomial infections^2-5.

Diabetic foot ulcer and surgical site infections have a long-term impact on increasing treatment cost, morbidity, and mortality. The pathogens isolated from wounds may vary depending upon the core problem, infection site location, and type of surgical strategy. Antimicrobial medicines play a major role in the treatment of wound infections. However, their extensive use, often overuse, and abuse increases the resistance to their efficacy. Therefore, one of the key challenges faced by the countries is to ensure rationale use of antibiotics. Antimicrobial resistance patterns are continually evolving, and multidrug-resistant organisms undergo progressive antimicrobial resistance, continuously updated data on antimicrobial susceptibility profiles will be essential to ensure the provision of safe and effective therapies^6-10.Therefore, the knowledge of the prevalence wound infections and their current antimicrobial profile become necessary in selecting appropriate empirical treatment of these infections. Our study aimed to determine the bacteriology of wound infections and to study the antibiotic susceptibility pattern of the isolates.

MATERIALS AND METHODS:

This prospective study was conducted for a period of 6 months, in a tertiary care Hospital, Erode. Written Ethical approval for this study was obtained from the Ethical Committee (JKKNCP/eth/pp/07/43), and informed consent was obtained from all patients. A total of 120 patients with wound infections such as ulcer wounds, diabetic foot ulcer wounds, post-operative wounds were enrolled in the study. All the patients were on empirical antibiotics therapy. Both male and female patients, patients of all age groups, and patients having wound infections with pus discharge, were included in this study. Patients with negative cultures and patients with opportunistic infection were excluded from this study. The pus swabs were obtained from in patients with wound infections. The superficial discharge was cleaned with normal saline, and the pus swab samples were obtained by applying pressure on the wound before applying antibacterial agents. Samples were processed for isolation (MacConkey Agar medium, Blood agar medium, Hichrome UTI agar medium) and identification of bacterial pathogens according to the standard microbiological techniques (Urease test, Triple sugar iron medium, Citrate test, Mannitol motility medium, Oxidase test)

Antimicrobial Susceptibility Testing:

The antimicrobial susceptibility testing of isolates were done as per the criteria of CLSI by Kirby Bauer disc diffusion method^11-14.From a pure culture, 3–4 selected colonies of microbe had been taken and transferred to a tube containing 5ml sterile nutrient broth and were mixed gently. Then a homogenous suspension was formed and incubated at 37°C until a visible turbidity obtained. Sterile cotton swab was utilized and the excess suspension was separated by gentle rotation of the swab against the surface of the tube. The swab was then used to allocate the bacteria uniformly over the entire surface of Mueller Hinton plate.

The inoculated plates were dried at room temperature for 3-5 minutes, and 8-9 sets of antibiotic discs with the following concentrations were then evenly distributed on the surface of a Muller Hinton plate: Amoxicillin (AML) (30μg), Ampicillin (AMP 10mcg), Penicillin G (P) (10μg), Erythromycin (E 15mcg), Gentamycin (GEN 10 mcg), Cotrimoxazole (COT 25mcg) and Vancomycin (VA 30mcg), Amikacin (AK 30mcg), Cefixime (CFM 5 mcg), Cefotaxime (CTX 30mcg), Piperacillin+ Tazobactum (PIT 10mcg), Imipenem (IPM 10mcg), Ciprofloxacin (CIP 5mcg), Meropenem (MRP 10mcg), Methicillin (MET 5mcg), Ceftazidime (CAZ 30mcg). Availability of antibiotics and frequent prescriptions for the management of wound infections in the hospital were used as the criteria for selecting antimicrobial agents to be tested. The plates were then incubated at 37°C for 24 hours. The diameter of zones of inhibition around the discs was measured to the nearest millimeter using a metal caliper. The isolates were classified as sensitive and resistant according to the standardized table supplied by the CLSI¹⁵.

RESULTS:

Out of 120 samples collected, 20 samples were excluded from the study for the reason of negative culture. Out of 100 culture positive samples, 61 samples were from diabetic ulcer patients, 20 samples were from ulcer patients, and 19 samples were from post-operative patients.

Table 1: Gender wise distribution of patients with wound infections (n=100)

Gender	Number of patients (n=100)	Percentage (%)
Male	63	63%
Female	37	37%

Table 2: Distribution pattern of samples isolated from different wound site (n=100)

Type of wound infections	Number of cases (n=100)	Percentage of cases
Diabetic foot ulcer	61	61%
Ulcer	20	20%
Surgical site infections	19	19%

Table 3: Organisms isolated from infection site (n=100)

Culture yielded single type microbe (n=71)	Culture yielded two type microbe (n=29)
71%	29%

Table 4: Culture that yielded single type organism from diabetic foot ulcer sites (n=47)

Organism	Number of cases (n=47)	Percentage (%)
S. aureus	18	49.18 %
E. coli	11	29.50 %
Proteus	10	21.31%
Pseudomonas aeruginosa	5	14. 75%
Klebsiella	3	08.19%

Table 5: Culture that yielded two type of organisms from diabetic foot ulcer sites (n=14)

Organism	Number of cases (n=14)	Percentage (%)
E. coli + S. aureus	4	28.57%
S. aureus + Pseudomonas	3	21. 42%
S. aureus + Proteus	2	14. 28%
S. aureus + Klebsiella	2	14. 28%
E. coli + Pseudomonas	1	07.10%
E. coli + Proteus	1	00. 10%
S. aureus + E. coli	1	07. 10%

Table 6: Culture that yielded one type of organism from ulcer sites (n=15)

Organisms	Number of cases (n= 15)	Percentage (%)
S. aureus	8	60 %
Proteus	3	30 %
E. coli	2	15 %
Klebsiella	2	15 %

Table 7: Culture that yielded two types of organisms from ulcer sites (n=5)

Organism	Number of cases (n= 5)	Percentage (%)
S. aureus + Proteus	2	40 %
Proteus + Klebsiella	1	20 %
S. aureus + Klebsiella	1	20 %
S. aureus+ E. coli	1	20 %

Table 8: Culture that yielded single type organism from surgical site infections (n=17)

Organism	Number of cases (n=17)	Percentage (%)
S. aureus	13	78. 94 %
Pseudomonas	3	15. 78%
E. coli	1	10.52%

Table 9: Culture that yielded two type organism from surgical site infections (n=2)

Organism

Number of cases

(n=2)

Percentage (%)

S. aureus + Klebsiella

50 %

S. aureus + E. coli

50 %

Table 10: Total number of organisms isolated from different wound infections (n=100)

Organisms	Number of cases (n=100)	Percentage (%)
S. aureus	57	57 %
E. coli	23	23 %
Proteus	19	19 %
Pseudomonas	13	13 %
Klebsiella	8	8 %

Table 11: Antimicrobial susceptibilities of bacteria isolated from different wound infection sites

Drugs	*S. aureus* *n=57**	*E. coli* *n= 23**	*Proteus* *n=19**	*Pseudomonas* *n= 13**	*Klebsiella* *n= 8**
Amikacin	29(39)	6(6)	4(10)	7(7)	3(5)
Cefixime	0(15)	0(5)	2(6)	0(6)	0(2)
Cefotaxime	11(35)	0(6)	2(12)	1(7)	0(5)
Piperacillin+ Tazobactum	4(4)	5(6)	8(8)	5(5)	2(3)
Imipenem	2(2)	6(6)	12(12)	7(7)	4(5)
Ciprofloxacin	13(24)	3(3)	6(14)	3(6)	1(5)
Meropenem	9(15)	6(6)	8(12)	3(6)	0(5)
Gentamycin	21(39)	4(6)	12(18)	4(7)	1(5)
Vancomycin	18(34)	NA	NA	NA	NA
Erythromycin	12(23)	1(1)	NA	NA	NA
Ampicillin	1(23)	NA	NA	0(1)	NA
Methicillin	6(23)	NA	NA	NA	NA
Ceftazidime	1(6)	0(5)	0(8)	0(7)	0(5)
Cotrimoxazole	3(3)	NA	NA	NA	NA

n*: The total number of bacteria isolated. The number of sensitive pathogen isolated is given first. The total number of bacteria tested for the antibiotics is in brackets.

DISCUSSION:

The incidence of wound infection was more common in males (63%) than in females (37%). Similar results were obtained by Ohalete et al¹⁶.Out of100 culture positive samples, 71% of samples showed one type of microbial growth, 29% samples showed two types of microbial growth. Samples isolated from diabetic ulcer sites mostly showed two types of microbial growth than samples isolated from ulcer cases and surgical site cases. In diabetic foot ulcer sites, necrotic tissue and low oxygen tension promote the proliferation of microbial growth^17,18. This may be one of the reason for variation in microbial growth in diabetic foot ulcer samples. These findings comply with the results in the study conducted by Anne et al¹⁹. The most frequently isolated organisms from diabetic foot ulcer sites were S. aureus (49.18%), followed by E. coli (29.50%), Proteus (21.31%), Pseudomonas aeruginosa (14.75%) and Klebsiella (8.19%). This result agrees with the the study conducted by Mohammed A et al., who reported that S. aureus is the most prevalent organism in the wound sites, accounting for almost 60% of the isolates^20-22.The most frequently isolated organisms from ulcer sites were S. aureus (60%), followed by Proteus (30%), Klebsiella and E. coli (15%). The second most prevalent organism isolated was Proteus.

In this study absence of pseudomonas was observed in samples isolated from the ulcer site. This may be due to organisms like Pseudomonas are not very invasive unless the patient is highly immunocompromised²³.Prevalence of S. aureusin the prospective data is in agreement with a previous studies^24-26. Out of 19 surgical site samples, 17 samples were showed one type of organism growth, and two samples were with two types of organism growth. The most frequently isolated organisms from surgical sites were S. aureus (78.94%), followed by Pseudomonas (15.78), E. coli (10.52%), and Klebsiella (5.26%). Surgical injuries will recover quickly if blood perfusion is expanded, thus delivering oxygen, then nutrients, and cells of the immune system to the site of injury and giving a negligible chance for microorganisms to colonize and multiply^27-29.In the case of the prevalence of isolated pathogens. S. aureus isolated from different wound sites shown high sensitivity pattern towards Imipenem (100%), Piperacillin – Tazobactum (100%) and Amikacin (74.35%), but it shown high resistance towards Cephalosporins [Cefixime (100%), Ceftazidime (83.33%)] and Methicillin (73.91%). E. coli isolated from different wound sites shown high sensitivity towards Ciprofloxacin (100%), Meropenem (100%), Erythromycin (100%), Imipenem (100%) and Amikacin (100%), while most of the isolates were resistant to Cephalosporins [Cefixime (100%), Cefotaxime (100%) and Ceftazidime (100%)]. Piperacillin – Tazobactum (100%), Imipenem (100%) and Gentamycin (66.66%) shown high sensitivity pattern towards Proteus isolated from different wound infection sites, while Cephalosporins [Ceftazidime (100%), Cefotaxime (83.33%) and Cefixime (66.66%)] shown resistant pattern towards the isolates. Pseudomonas isolated from different wound sites shown high sensitivity pattern towards Amikacin (100%), Imipenem (100%), Piperacillin – Tazobactum (100%), while it shown a high resistant pattern towards Cephalosporins [Cefixime (100%), Cefotaxime (85.71%)] and Meropenem (50%)]. Klebsiellae isolated from different wound sites shown high sensitivity pattern towards Imipenem (80%), Piperacillin (66.66%), and Amikacin (60%), while it demonstrated a high resistant pattern towards Cephalosporins [Cefixime (100%), Cefotaxime (100%), Ceftazidime (100%)].

The most commonly prescribed drugs for S. aureus infection in the study hospital were Cefotaxime (65.5%), Amikacin (34.4%), and Ampicillin (19.6%). But the drugs which are more sensitive to the organism were Cotrimoxazole (100%), Piperacillin - Tazobactam (80%), Imipenem (72.72%), and Gentamycin (62.245). For E. coli infection, commonly prescribed drugs in the study, hospital were Cefotaxime (70%), Gentamycin (37.5%), and Ciprofloxacin (25%). From the antibiotic susceptibility pattern, it was observed that the most sensitivity pattern of drugs was Imipenem (86.95%) followed by Amikacin (86.36%) and Gentamycin (72.27%). In the study site, the drugs prescribed empirically for Klebsiella infection were found to be Cefotaxime (77.7%), Ciprofloxacin (22.2%). Our study observed that Klebsiella sensitive to Amikacin (71.42%) and Imipenem (71.42%). Drugs prescribed empirically for Pseudomonas infection were Cefotaxime (100%), Amikacin and Gentamycin (30.76%). But drugs sensitive to the organism were found to Piperacillin -Tazobactam (100%), Imipenem (92.30%) and Amikacin (76.92%). Empirically prescribed drugs at the study site for Proteus infection were Cefotaxime (83.3%), Amikacin (44.4%). From the antibiotic susceptibility pattern study, it was observed that Imipenem (100%) more sensitive, followed by Piperacillin -Tazobactam (84.61%) and Ciprofloxacin (56.25%). Studies were reported the similar results^30-31.

The microorganisms isolated from diabetic foot ulcer samples were sensitive to Imipenem (84.9%), Amikacin (72.85%), Piperacillin -Tazobactum (68.57%), and Gentamycin (60.29%). But in the study site, the first line drugs prescribed diabetic foot ulcer asepsis were Azithromycin and Gentamycin. The second line drug of choice was Ampicillin. Cefotaxime and Amikacin were the third line drugs of choice. The microorganisms isolated from ulcer cases were sensitive to Imipenem (100%), Piperacillin -Tazobactum (100%), Amikacin (69.56%), and Gentamycin (60.86%). But the antibiotic policy of the study site recommended drugs Erythromycin, Amoxycillin, and Cloxacillin as first line drug of choice. The microorganisms isolated from surgical site infections were sensitive to Imipenem (83.3%), Piperacillin -Tazobactum (80%), and Amikacin (73.91%). But according to the antibiotic policy, Ampicillin and Gentamycin are the first line drugs for clean wound. While for a contaminated wound Cefotaxime and Amikacin are the drugs of choices^32-34. Organisms showed diversity in the sensitivity pattern towards the antibiotics tested, but there is no difference in sensitivity pattern observed according to the site of infection. From the above data it is clear that the sensitivity pattern of the antibiotics is not based on the infection site but on the type of organisms.

CONCLUSION:

This study gives us an insight to the current state of causative pathogens and their sensitivity to different antibiotics used in tertiary care hospital, Erode. The data of this study may be used to determine trends in antimicrobial susceptibilities, to modify antibiotic policy, update hospital formulary and overall to assist clinicians in the rational choice of antibiotic therapy to prevent misuse, or overuse, of antibiotics in tertiary care hospital, Erode.

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

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Received on 12.07.2021 Modified on 27.07.2021

Res. J. Pharmacology and Pharmacodynamics. 2021; 13(3):81-85.

DOI: 10.52711/2321-5836.2021.00017